# Gravity reading much lower than exected: why?

Okay, so my friend and me made an experiment yesterday. We wanted to brew a >20%, 300+ IBU IIPA.

Yeah yeah... I know :)

Now to the question. We used 10.5kg of grain for 26.25 liters of water for the mash. From the recipe calculator, we should have gotten around 1.208 OG. We "only" managed to get it to 1.120.

I wanted to ask if anyone had an idea of that poor efficiency. Mash went wonderfully at a temperature of 66°C.

• Is there some point where converting to sugars in mash gets a lot harder?
• Is there anything that you can think of that could create this result?

This is for a 3 gallons batch (11.5 liters).

Thanks!

• Is the 1.120 OG reading before or after you boiled the batch down to 11.5 liters? If that's after boiling down, then what was the gravity before you started boiling? 1.120 represents 89% efficiency with 10.5kg of grain in 26.25l of water. Apr 2 '14 at 15:52
• Using brewersfriend.com/brewhouse-efficiency, I get an efficiency of 43.18%. Apr 2 '14 at 16:04

Your efficiency goes down as the gravity of your beer goes up. That's because of the sugar you leave behind when using a "normal" amount of water. In order to increase your effieincy, you need to sparge more. That also means you need to boil longer to drive off the extra water.

• To me, this seems like the best explanation. We already boiled for 90 minutes, but I know we could have gotten more sugars by sparging more, and maybe boil it for 120 minutes instead. Apr 3 '14 at 12:21

Putting 10.5kg of grain in 11.5 litres of water will kill your efficiency, unfortunately:

From Braukaiser:

Traditional British style infusion mashes are with about 2-2.5 l/kg (1 - 1.15 qt/lb) very thick and German style mashes are generally much thinner (3.5-5 l/kg / 1.75-2.5 qt/lb). Historically this is rooted in the fact that the latter needed to be pumped and stirred.

In the limit of attenuation experiments it was shown that a 5 l/kg (2.4 qt/lb) mash showed much better conversion efficiency than a 2.5 l/kg (1.2 qt/lb) mash. This is also supported by anecdotal experience from home brewers who found that thin mashes generally lead to better overall efficiency.

Comparatively, you had 1.095 l/kg mash thickness. If you want to try again, I would recommend you read the 21% Alcohol All-Grain Beer article on byo.com. The author gets around the issue you encountered by using far, far more water (better conversion efficiency), then boiling it down to a usable final volume.

Good luck!

• Oh, what I meant by 11.5 liters is the final batch quantity! We actually used 2.5l/kg for the mash (editing my post now...) Apr 2 '14 at 15:41
• But thanks for your answer, it also lead to great information :) Apr 3 '14 at 13:18